The NE-CAT Center for Advanced Macromolecular Crystallography operates two undulator beamlines at Sector 24 of the Advanced Photon Source, Argonne National Laboratory. Our mission is to develop advanced technologies for challenging problems in structural biology. These problems come to us as Driving Biomedical Projects (DBPs), selected for their groundbreaking science. Examples include membrane channels, transporters, and receptors; cell signaling proteins; enzymes catalyzing complex cellular processes; structural biology of translation, transcription, recombination and repair; lare RNA molecules and RNA-mediated gene regulation, and large protein complexes such as nuclear pores. These projects often confront microcrystals, inhomogeneous crystals, poorly diffracting crystals, or pathologies such as multiple lattices. To address these problems we will develop technology in three interdependent areas: (1) microbeam diffraction, (2) beamline automation, and (3) low resolution structural biology. Microbeam diffraction builds on our successful microcrystal diffraction program. We will develop technology for small (2- 5 |j,m), intense and stable microbeams, for use with microcrystals and for measuring data from selected regions of inhomogeneous crystals. We will also work out how to improve sample stability, which often limits data quality. For inhomogeneous samples we will develop optimal data-collection protocols. Beamline automation will focus on new, rapid screening protocols, automated procedures to determine the best data collection strategies, especially for multiple crystals and flexible kappa geometry, and methods for automated data processing and analysis. Low resolution structural biology is growing rapidly, driven by structural studies of multicomponent complexes and membrane proteins. We will develop technology to obtain the best possible signal-to-noise at the resolution limit while still measuring the lowest order reflections. We will develop protocols to optimize data-collection strategies and data processing, especially for multiple crystals. We will also develop on- site methods to improve the resolution of existing crystals. During the past five years we have maintained a very productive collaboration and service program. We expect the number of users (including DBPs) to remain constant at about 1000 per year. We will make our new technology available to all users as early as possible. A strength of our Center is user training. We will continue our extensive training program, while developing new approaches to train remote access users. We will continue dissemination of both technology and scientific results through mechanisms that include our web site, presentations at meetings, workshops, publications, and one-on-one contacts.